Quark offered to give Odo a refund in this episode. But the very first rule of acquisition states that "Once you have their money, you never give it back."

Plotline

Quark sells Odo an injured baby Changeling; determined not to repeat the 'mistakes' made by his own educator, Odo detrmines to use kindness to teach the baby how to shapeshift. But as all his efforts fail, he mst face up to the fact that sometimes a father must be cruel to be kind.